Air carrier X had less than standard separation from aircraft Y. System error.

Attributes
ACN	187038
Time
Date	199108
Day	Thu
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : osi
State Reference	CA
Altitude	msl bound lower : 10000 msl bound upper : 10000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : oak
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	climbout : intermediate altitude cruise other
Route In Use	enroute : on vectors
Flight Plan	IFR
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	cruise other
Route In Use	enroute : direct
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 180 flight time total : 18000 flight time type : 1800
ASRS Report	187038
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 180 flight time total : 5000 flight time type : 1700
ASRS Report	187289
Events
Anomaly	conflict : airborne less severe non adherence : required legal separation non adherence : published procedure
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	flight crew : took evasive action
Consequence	Other
Miss Distance	horizontal : 12000 vertical : 0
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Air carrier X were level at 10000 ft as assigned by ATC. We visually noted traffic at 12 O'clock approximately 20 mi but could not tell if it was level at our altitude. Our TCAS was set at range 10 and alerted us that aircraft Y was at our altitude. The closure rate was high, thus a RA was commanded by our TCAS and we responded with a 1000 ft climb. Supplemental information from acn 187289. Determining the intruding acfts approach, a climbing right turn was required to avoid a conflict. This solution was followed by a TCAS command. TCAS performed perfect and ATC had assigned us the wrong altitude of 10000 instead of 11000.

Original NASA ASRS Text

Title: ACR X HAD LTSS FROM ACFT Y. SYS ERROR.

Narrative: ACR X WERE LEVEL AT 10000 FT AS ASSIGNED BY ATC. WE VISUALLY NOTED TFC AT 12 O'CLOCK APPROX 20 MI BUT COULD NOT TELL IF IT WAS LEVEL AT OUR ALT. OUR TCAS WAS SET AT RANGE 10 AND ALERTED US THAT ACFT Y WAS AT OUR ALT. THE CLOSURE RATE WAS HIGH, THUS A RA WAS COMMANDED BY OUR TCAS AND WE RESPONDED WITH A 1000 FT CLB. SUPPLEMENTAL INFO FROM ACN 187289. DETERMINING THE INTRUDING ACFTS APCH, A CLBING R TURN WAS REQUIRED TO AVOID A CONFLICT. THIS SOLUTION WAS FOLLOWED BY A TCAS COMMAND. TCAS PERFORMED PERFECT AND ATC HAD ASSIGNED US THE WRONG ALT OF 10000 INSTEAD OF 11000.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.